Fuel feeding method and apparatus

ABSTRACT

The height of a cone, mound, or pile of fuel in the combustion area of a furnace is controlled by arranging a temperature sensor on a portion of a probe normally penetrating the burning fuel. When the fuel burns down sufficiently to expose the sensor to direct heat from the pile, a signal is sent from the sensor to a relay which opens a valve mechanism to feed fuel into the furnace. A timer may be used to limit the amount of fuel delivered.

United States Patent 1191 Midkiff 1 July 9, 1974 [5 FUEL FEEDING METHOD AND 3,281,518 10/1966 Stroud et al. 73/359 APPARATUS 3,298,338 1/1967 Clark, Sr 110/101 Cecil L. Midkiff, PO. Box 308, Edmonds, Wash. 98020 22 Filed: Apr. 10, 1973 21 App]. No.: 349,756

[76] Inventor:

{52] US. Cl 110/101 CD, 236/15 B, 73/359 [51] Int. Cl F23k 3/22 [58] Field of Search 110/101 R, 101 CD; 236/15 B; 73/359 [56] References Cited UNITED STATES PATENTS 2,215,067 9/1940 Denison et al 110/101 2,870,233 1/1959 Comer 73/359 X 3,232,794 2/1966 Korton 73/359 X Primary Examinerl(enneth W. Sprague Attorney, Agent, or FirmClarence A. OBrien; Harvey B. Jacobson [5 7] ABSTRACT The height of a cone, mound, or pile of fuel in the combustion area of a furnace is controlled by arranging a temperature sensor on a portion of a probe normally penetrating the burning fuel. When the fuel burns down sufficiently to expose the sensor to direct heat from the pile, a signal is sent from the sensor to a relay which opens a valve mechanism to feed fuel into the furnace. A timer may be used to limit the amount of fuel delivered.

9 Claims, 4 Drawing Figures mmmm 91914 3.822.655?

SHEET 10F 2 Fig.

PATENTEUML 9 i974 SHEET 2 OF 2 I20 VAC Relay 48 Thermocouple W 1 FUEL FEEDING METHOD AND APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to feeding a material on demand, and particularly to the regulation of the height of a cone, mound, or pile of fuel arranged in the combustion area of a furnace.

2. Description of the Prior Art Many methods of controlling the rate of feeding solid fuels such as hog fuel, saw-dust, planar shavings, and the like, into Dutch oven type boilers, and the like, have been used in the past. The old hand-fired method is the most common. Fuel travels along an overhead conveyor, and is selectively dropped through a chute into the top of the furnace by an operator manually controlling the flow of fuel with trap doors, and the like. Very poor control, especially of steam, and lots of smoke is the end result of these known approaches. Sight transmitters and receivers are being used which sight across the top of the fuel and maintain a desired fuel height by means of relays and air cylinders that actuate the fuel release mechanisms. The known arrangements of this kind function satisfactorily when used with single boiler installations and with single fuel piles per boiler. On multiple boiler installations and with two or more fuel cones or piles in each furnace, however, the installation of the sighting heads becomes increasingly difficult, and inordinately complex.

A thermostatically controlled sensing unit using a liquid such as water as a control source has also been proposed. Such a unit is shown in US. Pat. No. 3,298,338. This approach, however, requires a constant supply of water at high volume. Interruption of the water flow would most likely cause the unit to malfunction and could burn out the sensing bulb. Further, ecology pollution problems will frequently require that the heated water being discharged from the system be cooled before its ultimate disposal. This, of course, adds to the cost and decreases the economic efficiency of the system. This is also the case with the numerous valves, strainers, plumbing, and drain connectors required for the liquid flow system. In addition, it has been found that the probes continually fill up with lime deposits, and the like, and have to be cleaned frequently in order to maintain their sensitivity and prevent them from burning out. The heat is frequently so intense on the exposed portion of the probethat is, the portion of the probe above the fuel pilethat the liquid, or water, temperature is raised sufficiently to actuate an associated thermostatic relay before the height of thepile is reduced enough for the sensing bulb to become exposed to the direct heat of the fuel pile. Thus, the fuel height may vary as much as two feet or more, when 4 under ideal conditions the fuel cone height should not vary more than four to six inches. As a result, constant attendance is required to compensate for this problem and maintain the fuel cone height within optimum limits. 7

SUMMARY OF THE INVENTION 7 It is an object of the present invention to provide a simple, reliable, and more accurate method and apparatus for controlling the feed of fuel onto a cone, mound, or pile arranged in the combustion area of a furnace for regulating the height of the cone, mound, or pile.

It is another object of the present invention to provide a thermostatic control for a furnace fuel feeding system.

It is yet another object of the present invention to provide a fuel feeding system that eliminates liquid plumbing and its associated valves and drain, can minimize the risk of bum-out, has substantially constant sensitivity, is rugged and of simple construction, is easy of installation, may be adjusted to vary a volume of fuel added in each operating cycle, requires a minimum of supervision, and generally reduces maintenance and increases efficiency of a plant with which the system is associated.

These and other objects are achieved according to the present invention by providing a thermostatic control having: a probe inserted into a combustion area of a furnace and normally having a portion penetrating a pile of burning fuel in the combustion chamber; a temperature sensor carried by the probe for sensing a temperature in the combustion area; and an arrangement regulated by the temperature sensor for feeding fuel into the combustion area in response to a signal from the temperature sensor indicative of the pile having decreased to a predetermined height exposing the temperature sensor to direct heat from the pile.

Advantageously, the temperature sensor is a thermocouple arranged on a portion of the probe normally penetrating the pile of burning fuel. A preferred embodiment of the probe itself has a tube provided with spaced ends and filled with a heat insulating material, such as a refractory material.

The fuel feeding arrangement advantageously includes a valve mechanism arranged for selectively blocking and unblocking a fuel flow path to the furmace, and a relay connected to the valve mechanism and to the probe temperature sensor. The relay is arranged for actuating the valve mechanism to unblock the fuel flow path in response to a signal received from the temperature sensor. A timer may be associated with the relay for interrupting the latter a predetermined length of time after a signal from the temperature sensor causes fuel to pass the valve mechanism. By adjusting the time delay caused by this timer to terminate the fuel flow, the height of the fuel pile can be maintained within desired limits.

A fuel feeding system according to the present invention controls the feed of fuel by placing a signaltransmitting temperature sensor in a pile of burning fuel arranged in a combustion area of a furnace, and

' supplying fuel to the furnace when the sensor transmits a signal indicative of the fuel pile being reduced to a level beneath the sensor.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings, fonning a part hereof, wherein like numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary, partly schematic, vertical sectional view'showing a furnace provided with a fuel feeding system according to the present invention.

FIG. 2 is a fragmentary, side elevational view, partly broken away and in section, showing a sensing probe according to the present invention.

FIG. 3 is a sectional view taken generally along the line 33 of FIG. 2.

FIG. 4 is a schematic diagram showing an electrical wiring circuit according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 of the drawings shows a conventional furnace 10, which may be an industrial furnace or incinerator, provided with a combustion area 12. The furnace illustrated in FIG. 1 of the drawings is a conventional underfired Dutch oven type of furnace having a firebox in front of a boiler (not shown), and constructed to permit maximum temperatures in combustion area 12 of, for example, 2,000F. A fuel cone, mound, or pile 14 is arranged on conventional grates 16 in combustion area 12. The solid line indicating the extent of pile 14 is the maximum height of the pile, while the dotted line is its minimum height. These heights may be adjusted as will be discussed below. A throat 18 provides a passage for the combustion flame (not shown) and gases into the heat transfer area of the boiler associated with the furnace. A conventional fuel conveyor 20 communicates by means of a trap-door kind of valve mechanism 22 with a fuel chute 24 leading to an opening 26 in the top of furnace 10. A sensing unit 28 according to the present invention is adjustably mounted in chute 24 as by a conventional clamp 30 so as to extend through opening 26.

Valve mechanism 22, which is arranged for selectively blocking and unblocking the fuel flow path to the furnace as defined by conveyor 20 and chute 24, is provided with a conventional trap-door gate 31, a fluid motor 32, which may be a conventional piston and cylinder motor, and fluid lines 34 and 36 connected to motor 32 for supplying actuating fluid, preferably air, to this motor. A, for example, solenoid operated fluid valve 38 of known construction is arranged between lines 34, 36 and a fluid supply line 40 for controlling flow in lines 34 and 36 in response to valve 38 being energized by an arrangement to be discussed below. Supply line 40 may be connected to any conventional supply of operating fluid, such as a conventional air compressor.

A probe 42 inserted into combustion area 12 of a furnace 10, is so arranged that a portion thereof normally penetrates a pile of burning fuel, such as pile 14, arranged in combustion area 12. This probe 42 is formed by a tube 44, preferably a cylindrical tube constructed from a high-strength non-magnetic nickel-chromiumiron alloy such as are commonly available on the market and can withstand temperatures up to 2,200F. under appropriate conditions. It is to be understood that other, suitable materials may be substituted for this kind of metal if desired. A heat-insulating material 46 substantially fills tube 44 between the spaced ends of the latter, and a conventional thermocouple 48 is arranged in a sleeve 49, which may be constructed from a material similar to that used for tube 44, and is fastened to a closed end of tube 44 as by welding, and the like. If desired, thermocouple 48 may be entirely embedded in material 46, but it has been found advantageous to arrange the thermocouple in a sleeve such as that designated 49 and have it extend beyond the end of sleeve 49 so as to be in direct contact with the fuel in pile 14. Leads 50 and 52 of thermocouple 48 are embedded in and extend through material 46, as can readily be seen from FIG. 3 of the drawings.

A housing is shown mounted on the top of probe 42 to cooperate with the latter in forming a sensing unit 28. It is to be understood, however, that the equipment, to be set out immediately below, housed in housing 54 may be situated at a location remote from probe 42 and connected to the probe as by, for example, flexible, rubber covered, thermocouple wire of a conventional nature. A relay 56 is illustrated as arranged in housing 54, and is connected to valve 38 of valve mechanism 22 and to thermocouple 48. The particular connection of relay 56, which may be a conventional temperature controller with a deviation indicator in the range of, for example, 0 to 1,400F., is arranged for actuating valve 38 to unblock the fuel flow path through chute 24 in response to a signal from thermocouple 48. A four-wire power cord 58 is shovm extending from housing 54 to connect relay 56 to solenoid operated valve 38 and a conventional source of electric power. An optional feature of the present invention which may be advantageous under certain circumstances is the provision of a conventional timer 60 selectively connectible to relay 56 as by a single pole, double throw switch 62, also of a conventional construction, for interrupting the circuit completed through relay 56 a predetermined time after a signal from thermocouple 58 causes relay 56 to close and pass fuel by valve mechanism 22. A conventional four-line connector 64 (FIG. 1) provides mating male and female connector elements to selectively connect sensing unit 28 to the remainder of the fuel feeding system.

FIG. 4 of the drawings shows a diagram of an electrical circuit for the present invention. Positioning of switch 62 to either the auto or on positions from the off position, and placing thermocouple 48 in a pile 14, proper dimensioning of the components will cause an electrical signal to be generated by thermocouple 48 when pile 14 has burned down sufficiently to expose thermocouple 48 to direct heat from pile 14, indicated by the broken lines in FIG. 1 of the drawings, which is sufficiently strong enough to actuate relay 56 and close a circuit from a conventional power source, such as any standard volt ac source, through relay 56 and to the solenoid of valve 38 for energizing same and opening gate 31. If timer 60 is included in the circuit, which otherwise would eliminate the need for the auto position of switch 62, this timer may be set to open or interrupt the circuit through relay 56 after the lapse of a predetermined length of time. If timer 60 is not in the circuit, or switch 62 is set to the on position, relay 56 will interrupt the circuit after the fuel has cooled thermocouple 48 by piling up around same. Positioning of probe 42 by clamp 30 will also permit adjustment of the height of pile 14, either independently or in conjunction with a timer.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and de scribed, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

l. A thermostatic control for a furnace fuel feeding system comprising, in combination:

a. a probe arranged inserted into a combustion area of a furnace and normally penetrating a pile of burning fuel in the combustion area;

b. means carried by the probe for sensing a temperature in the combustion area; and

c. means regulated by the sensing means for feeding fuel into the combustion area in response to a signal from the sensing means, the signal being indicative of the pile having decreased to a predetermined height, the sensing means being a thermocouple arranged on a portion of the probe normally penetrating the pile of burning fuel, and the predetermined height exposing the thermocouple to direct heat from the pile.

2. A structure as defined in claim 1, wherein the probe includes a tube having spaced ends and filled with a heat insulating material, and the thermocouple is arranged adjacent an end of the tube.

3. A structure as defined in claim 1, wherein the means for feeding fuel includes:

i. a valve mechanism arranged for selectively blocking and unblocking a fuel flow path to the furnace; and

ii. a relay connected to the valve mechanism and the probe thermocouple, and arranged for actuating the-valve mechanism to unblock the fuel flow path in response to a signal from the thermocouple.

4. A structure as defined in claim 3, wherein the valve mechanism includes a gate, a fluid motor connected to the gate, fluid lines connected to the fluid motor for actuating same, and a solenoid operated fluid valve connected to the relay and fluid lines and arranged for controlling flow in the lines as a function of an operating mode of the relay.

5. A structure as defined in claim 4, wherein the means for feeding fuel further includes a timer selectively connectible to the relay and arranged for interrupting the relay a predetermined time after a signal from the thermocouple causes fuel to pass by the valve mechanism.

6. A structure as defined in claim 5, wherein the timer and relay are mounted on the tube at the end spaced from the end adjacent the thermocouple to form a unit with the probe.

7. A structure as defined in claim 3, wherein the means for feeding fuel further includes a timer selectively connectible to the relay and arranged for interrupting the relay a predetermined time after a signal from the sensing means causes fuel to pass by the valve mechanism.

8. A method for controlling the feed of fuel into a furnace, comprising the steps of:

a. placing a signal-transmitting temperature sensor in a pile of burning fuel arranged in a combustion area of a furnace; and

b. supplying fuel to the furnace when the sensor transmits a signal indicative of the fuel pile being reduced to a level beneath the sensor.

9. A method as set out in claim 8, wherein placing step (a) includes the step of penetrating the sensor into an upper portion of the fuel pile, and the supplying step (b) includes the step of terminating the fuel supply after a predetermined length of time. 

1. A thermostatic control for a furnace fuel feeding system comprising, in combination: a. a probe arranged inserted into a combustion area of a furnace and normally penetrating a pile of burning fuel in the combustion area; b. means carried by the probe for sensing a temperature in the combustion area; and c. means regulated by the sensing means for feeding fuel into the combustion area in response to a signal from the sensing means, the signal being indicative of the pile having decreased to a predetermined height, the sensing means being a thermocouple arranged on a portion of the probe normally penetrating the pile of burning fuel, and the predetermined height exposing the thermocouple to direct heat from the pile.
 2. A structure as defined in claim 1, wherein the probe includes a tube having spaced ends and filled with a heat insulating material, and the thermocouple is arranged adjacent an end of the tube.
 3. A structure as defined in claim 1, wherein the means for feeding fuel includes: i. a valve mechanism arranged for selectively blocking and unblocking a fuel flow path to the furnace; and ii. a relay connected to the valve mechanism and the probe thermocouple, and arranged for actuating the valve mechanism to unblock the fuel flow path in response to a signal from the thermocouple.
 4. A structure as defined in claim 3, wherein the valve mechanism includes a gate, a fluid motor connected to the gate, fluid lines connected to the fluid motor for actuating same, and a solenoid operated fluid valve connected to the relay and fluid lines and arranged for controlling flow in the lines as a function of aN operating mode of the relay.
 5. A structure as defined in claim 4, wherein the means for feeding fuel further includes a timer selectively connectible to the relay and arranged for interrupting the relay a predetermined time after a signal from the thermocouple causes fuel to pass by the valve mechanism.
 6. A structure as defined in claim 5, wherein the timer and relay are mounted on the tube at the end spaced from the end adjacent the thermocouple to form a unit with the probe.
 7. A structure as defined in claim 3, wherein the means for feeding fuel further includes a timer selectively connectible to the relay and arranged for interrupting the relay a predetermined time after a signal from the sensing means causes fuel to pass by the valve mechanism.
 8. A method for controlling the feed of fuel into a furnace, comprising the steps of: a. placing a signal-transmitting temperature sensor in a pile of burning fuel arranged in a combustion area of a furnace; and b. supplying fuel to the furnace when the sensor transmits a signal indicative of the fuel pile being reduced to a level beneath the sensor.
 9. A method as set out in claim 8, wherein placing step (a) includes the step of penetrating the sensor into an upper portion of the fuel pile, and the supplying step (b) includes the step of terminating the fuel supply after a predetermined length of time. 